smartdict.py revision 13714
1# Copyright (c) 2005 The Regents of The University of Michigan 2# All rights reserved. 3# 4# Redistribution and use in source and binary forms, with or without 5# modification, are permitted provided that the following conditions are 6# met: redistributions of source code must retain the above copyright 7# notice, this list of conditions and the following disclaimer; 8# redistributions in binary form must reproduce the above copyright 9# notice, this list of conditions and the following disclaimer in the 10# documentation and/or other materials provided with the distribution; 11# neither the name of the copyright holders nor the names of its 12# contributors may be used to endorse or promote products derived from 13# this software without specific prior written permission. 14# 15# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 18# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 19# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 21# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 25# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26# 27# Authors: Nathan Binkert 28 29# The SmartDict class fixes a couple of issues with using the content 30# of os.environ or similar dicts of strings as Python variables: 31# 32# 1) Undefined variables should return False rather than raising KeyError. 33# 34# 2) String values of 'False', '0', etc., should evaluate to False 35# (not just the empty string). 36# 37# #1 is solved by overriding __getitem__, and #2 is solved by using a 38# proxy class for values and overriding __nonzero__ on the proxy. 39# Everything else is just to (a) make proxies behave like normal 40# values otherwise, (b) make sure any dict operation returns a proxy 41# rather than a normal value, and (c) coerce values written to the 42# dict to be strings. 43 44from __future__ import print_function 45from __future__ import absolute_import 46 47from .convert import * 48from .attrdict import attrdict 49 50class Variable(str): 51 """Intelligent proxy class for SmartDict. Variable will use the 52 various convert functions to attempt to convert values to useable 53 types""" 54 def __int__(self): 55 return toInteger(str(self)) 56 def __long__(self): 57 return toLong(str(self)) 58 def __float__(self): 59 return toFloat(str(self)) 60 def __bool__(self): 61 return toBool(str(self)) 62 # Python 2.7 uses __nonzero__ instead of __bool__ 63 __nonzero__ = __bool__ 64 def convert(self, other): 65 t = type(other) 66 if t == bool: 67 return bool(self) 68 if t == int: 69 return int(self) 70 if t == long: 71 return long(self) 72 if t == float: 73 return float(self) 74 return str(self) 75 def __lt__(self, other): 76 return self.convert(other) < other 77 def __le__(self, other): 78 return self.convert(other) <= other 79 def __eq__(self, other): 80 return self.convert(other) == other 81 def __ne__(self, other): 82 return self.convert(other) != other 83 def __gt__(self, other): 84 return self.convert(other) > other 85 def __ge__(self, other): 86 return self.convert(other) >= other 87 88 def __add__(self, other): 89 return self.convert(other) + other 90 def __sub__(self, other): 91 return self.convert(other) - other 92 def __mul__(self, other): 93 return self.convert(other) * other 94 def __div__(self, other): 95 return self.convert(other) / other 96 def __truediv__(self, other): 97 return self.convert(other) / other 98 99 def __radd__(self, other): 100 return other + self.convert(other) 101 def __rsub__(self, other): 102 return other - self.convert(other) 103 def __rmul__(self, other): 104 return other * self.convert(other) 105 def __rdiv__(self, other): 106 return other / self.convert(other) 107 def __rtruediv__(self, other): 108 return other / self.convert(other) 109 110class UndefinedVariable(object): 111 """Placeholder class to represent undefined variables. Will 112 generally cause an exception whenever it is used, but evaluates to 113 zero for boolean truth testing such as in an if statement""" 114 def __bool__(self): 115 return False 116 117 # Python 2.7 uses __nonzero__ instead of __bool__ 118 __nonzero__ = __bool__ 119 120class SmartDict(attrdict): 121 """Dictionary class that holds strings, but intelligently converts 122 those strings to other types depending on their usage""" 123 124 def __getitem__(self, key): 125 """returns a Variable proxy if the values exists in the database and 126 returns an UndefinedVariable otherwise""" 127 128 if key in self: 129 return Variable(dict.get(self, key)) 130 else: 131 # Note that this does *not* change the contents of the dict, 132 # so that even after we call env['foo'] we still get a 133 # meaningful answer from "'foo' in env" (which 134 # calls dict.__contains__, which we do not override). 135 return UndefinedVariable() 136 137 def __setitem__(self, key, item): 138 """intercept the setting of any variable so that we always 139 store strings in the dict""" 140 dict.__setitem__(self, key, str(item)) 141 142 def values(self): 143 for value in dict.values(self): 144 yield Variable(value) 145 146 def items(self): 147 for key,value in dict.items(self): 148 yield key, Variable(value) 149 150 def get(self, key, default='False'): 151 return Variable(dict.get(self, key, str(default))) 152 153 def setdefault(self, key, default='False'): 154 return Variable(dict.setdefault(self, key, str(default))) 155 156__all__ = [ 'SmartDict' ] 157